A case-control study of ovarian cancer is involving 400 patients with this disease and 400 controls selected from the general population. The pathology for each case will be reviewed and classified according to specific histologic type by a recognized expert in ovarian cancer pathology. Personal, home interviews will be conducted to assess a variety of epidemiologic factors including general medical and family history, occupation, tobacco and alcohol habits, pregnancies, breast feeding, contraceptive experience, and drug use, including intrauterine exposure to drugs for the younger subjects. We will estimate the total number of ovulatory cycles as well as the longest series of consecutive ovulatory cycles uninterrupted by pregnancy, lactation, or oral contraceptive use and determine whether these measures correlate with ovarian cancer risk. Also of major interest are the relative risks associated with the use of oral contraceptives and hormones for the menopause. A doubling risk of cancer associated with several of the risk factors under study will be detectable in sub-groups of ovarian cancer of size 75 or more. Our goal is to identify risk factors that may be modified to reduce disease occurrence primarily or that may be of clinical usefulness in defining the woman at risk of ovarian cancer to achieve better control of the course of the disease secondarily.